A record price for a London home has been set with the £80million sale of a large detached house in Kensington.

It smashes the previous high of £67million for steel magnate Lakshmi Mittal's home in Kensington Palace Gardens and is claimed to be the world's most expensive single residential dwelling.

Contracts for the five-storey house in Upper Phillimore Gardens are believed to have been exchanged in recent weeks. The buyer is thought to be Ukrainian businesswoman and philanthropist Elena Franchuk, a friend of Sir Elton John.

The record sale price suggests that the global credit crunch is yet to hurt the pinnacle of the property market.

However, it may only stay as the record for a matter of weeks. A six storey house in Belgrave Square is due to come on the market in the spring for about £90 million.

The Victorian villa, not far from Kensington High Street, has been rebuilt and refurbished at an estimated £10 million and is not ready for occupation.

Builders have for the last 18 months been installing an underground swimming pool, gym, sauna and cinema.

Due to be completed in April, the house has at least 10 bedrooms and a secure "panic room".

The whole of Upper Phillimore Gardens currently resembles a building site, with diggers, cranes and delivery trucks clogging the road. Two other massive construction projects are under way.

The property, 17 Upper Phillimore Gardens, was bought for £20 million in June 2006 by a company called Coll Hill Spink 2, controlled by developer Mike Spink, who specialises in top end properties.

The previous owners, thought to be Chinese, bought it in 1997 and before that it was a girls' preparatory school.

The work is said to have upset neighbours, who include the Mayor of Moscow and his wife. The complaints concern noise and disturbance from the cranes and lorries which have been driving over the pavements, cracking flagstones and damaging public areas.

Ms Franchuk, the daughter of a former Ukrainian president and married to oligarch industrialist Viktor Pinchuk, has long been involved in charitable activities in her home country.

In 2003, she established the first and sole foundation in Ukraine committed to fighting HIV and Aids, aimed at drawing attention of opinion makers, government and business leaders to the problem.